Managing pastures for goats

Discusses types of forages, stocking rates and forage quality relevant to goats.
Includes a basic description of forage growth from vegetation to reproduction.
Describes how to utilize pasture and weed forages to maximize the objectives of the goat enterprise.
Different management steps should be taken if goats are used primarily for weed control than if they are used for milk or meat.

Introduction

Dairy goats depend on forages to meet their nutritional needs if they are to be economically viable. Forages commonly utilized are; grasses, browse, weeds, forbs, and seasonally; small grains, hays, and silages. With rare exception, all these plants contain usable protein, energy, minerals and vitamins in useful measure. It should be emphasized that goats actually prefer to browse on brush rather than on grass, commonly taking about 60% browse and 40% grass in mixed plant populations.

Since goats are particularly adept at selecting the most nutritious plants (and within plants, the most nutritious portions), they may do reasonably well on grazing areas considered poor to fair by man and cow alike if, of course, the amount of herbage is adequate. Like other animals, however, goats respond quite favorably to increased quality/quantity of feedstuffs. Public perceptions to the contrary, goats cannot in fact economically turn low quality vegetative matter into meat and milk. Successful managers know this; novices may not last long enough to learn it.

Composition of Forages

The composition of forages commonly eaten by goats varies widely. In practical grazing situations, goats consume an ever-changing combination of these feedstuffs with selection reflecting seasonal availability's and relative palatability's. The daily dry matter intakes of mature goats range between 3-5% of body weight, occasionally higher. The actual quantity of feedstuffs eaten per day will be influenced by physiological needs, palatability, dry matter content, digestibility, and rate of passage from the rumen.

When comparing the protein, total digestible nutrients (TDN) and mineral values of forages, several differences can be noted. First, legumes such as alfalfa, cowpea, lespedeza and vetch are higher in protein and calcium than non-legumes such as bermudagrass, bluestems, johnsongrass, sudangrass and lovegrass, either as grazing or as hay crops; their TDN values, however, are fairly comparable. Secondly, forages consumed by grazing, due to animal selection, are higher quality then hay from the same field. Thirdly, roughages are relatively higher in calcium than in phosphorus, while feed grains generally have more phosphorus than calcium. The mineral needs of meat goats are such that a need for phosphorus supplementation is much more likely than a need for extra calcium except perhaps during early lactation. Fourthly, protein and TDN levels of individual roughages are dependent on several variables, among them: age of the plant, soil fertility, rainfall, harvesting procedures, storage conditions, and variety. However, maturity (age) of the forage crop is the single greatest influence of quality.

Note that the protein and TDN contents of most browse plants are quite comparable with those of more traditional southern forages. As noted before, goats are particularly adept at selecting the most palatable parts of browse plants; fortunately, palatability is generally associated with lower fiber, higher protein and increased digestibility. Spring growth is typically the most palatable and therefore has the highest nutrient value. Browse plants, particularly those grown in forested areas, may produce significantly less quantity of forage per acre than native or improved pastures, but initial quality of browse may be a compensating consideration. Pine and oak forest under-story brush is a variable mixture of plants, many of which are good sources of protein and TDN for goats.

Stocking Rates

To evaluate the usefulness of pasture and browse plants for meat goat enterprises, it would be helpful to know their average annual yields per acre in addition to their protein and TDN content. Unfortunately, such data are scarce and, in any case, yields can vary very widely across time and place. Thus, it is very difficult to answer basic management questions concerning grazing density (head/acre), optimum grazing pattern (frequency and duration), and needs for supplemental feeding (protein, energy and minerals). For novice goat owners, the experiences of goat-owning neighbors are likely to be the best guidelines available.

Several rules of thumb for grazing can be typically applied, e.g., 6 mature goats equal 1 cow on native or improved pastures or 10 goats equal 1 cow on browse or brushy areas (as goats will utilize more of the brush and browse). As a practical matter, goat owners have rotationally grazed 10-12 goats per acre of good wheat pasture and 12-15 (occasionally more) goats per acre on alfalfa pastures. Some producers have reported grazing densities of 2-3 head per acre on good native pastures and 1-2 head per acre of brushy fields.

Forage Quality

Opinions are many and varied when discussing forage quality. The use of many different terms used in describing forage quality further complicates this topic, especially when discussing hay. For example, the color of a hay bale is frequently suggested as an indicator of the quality of the hay as a feedstuff, but hay color has almost no relationship to animal performance. This is the basis of an important fact: the only true measure of forage quality is animal performance. Quality is important only because it relates to animal performance.

Plants are made up of cells which are composed of cell walls and the contents within the cell walls. The intracellular contents can be assumed to be near 100% digestible, and digestibility does not change as the plant ages or grows. However, the chemical makeup of cell walls does change as the plant grows. With aging, the fiber content increases as a percent of the total plant. One complication is that there are several types of fiber in plants, and they can vary greatly in digestibility. We use the term increasing fiber to mean decreasing digestibility. Lignin, a fiber which is basically indigestible, increases rapidly as the plant matures, particularly if it begins reproductive growth.

Digestibility and Fiber Analysis

Digestibility can be viewed as a simple balance. If an animal is fed 10 pounds of dry hay and four pounds of dry manure is produced, then the hay is 60% digestible. The more digestible the forage, the more energy the animal obtains from the forage.

Currently most laboratories chemically determine the percent Acid Detergent Fiber (ADF) and/or Neutral Detergent Fiber (NDF) to predict the energy content, Total Digestible Nutrients (TDN), metabolizable energy (ME), and/or net energy (NE). NDF is a chemical estimate of the plant cell wall content of a forage and ADF is the cell wall content minus a cell wall component called hemicellulose. As a plant matures the cell wall content increases as a percent of the total plant cell. Plant cell walls are much less digestible than other parts of the cell (intracellular contents), accordingly, as the cell wall component of the cell increases with maturity, digestibility or quality of the forage decreases. Thus, a forage with a low NDF or ADF content is higher in quality than one with a high NDF or ADF content.

NDF is closely associated with total potential intake of the forage by an animal while ADF is more closely related to digestibility of the forage. Therefore, both values are used in predicting forage quality. Generally, most laboratories are using NDF or ADF along with crude protein (CP) content to predict the overall quality of forage samples. (An additional quality factor in forages is the mineral content; this aspect of quality is justifiably receiving more attention now than in the past.)

In general, as crude protein increases in a forage, livestock perform better (i.e., gain more weight, produce more milk, etc.). Thus, there is a reasonably good relationship between forage quality and CP content. However, there are several problems with CP as a predictor of animal performance. The first is the concept of first limiting nutrient. Put simply, if an animal is deficient in energy, any amount of protein in excess of requirements will do little to increase performance. The excess protein can be converted to an energy source by the animal, but this is a very expensive way to meet energy requirements. For example, if an animal has a crude protein requirement of 12%, then a forage with 15% CP will do little to increase performance. As always there are exceptions, which here concern some relatively difficult concepts involving amino acid (the building blocks of protein) balance, rumen protein bypass, and the relationship between higher protein and energy in forages. Although protein content of forages is important, energy is often more of a concern.

Forage Quality Components

The next step in understanding forage quality is to achieve a more thorough understanding of where the quality components of a forage are located in the plant. Previously, forage quality was discussed as it related to chemical assays and plant cellular components; but how does this relate to the whole plant and its parts? In general, most usable nutrients in a plant, at least the above ground parts, are in the leaves rather than in the stem. This is true of both grasses and broadleaf species, such as bermudagrass, tall fescue, alfalfa, clovers, dewberry/blackberry briars, honeysuckle, and kudzu. Further, the older or more mature the plant, the more this is true. For example, an alfalfa plant may analyze 31% ADF and 18% CP, but if the leaves and stems were separated and analyzed, the leaves might be 23% ADF and 26% CP, while the stems might be 37% ADF and 11% CP. This is the basis of the expression "manage for leafiness." Therefore, the leaf/stem ratio of forage is a reasonably good indicator of forage quality. As the leaf/stem ratio increases (i.e., more leaf), the quality of the forage increases accordingly.

Anti-Quality Components

Another factor involved in the feeding value of forage is the presence of anti-quality components. We deal with many of these factors. The alkaloids produced by the endophytic fungus of tall fescue are an example of one common anti-quality factor. Cattle performance on tall fescue has often been poorer than what was predicted or expected based on CP, TDN, etc., because of these alkaloids. Unfortunately the effect(s) of the tall fescue endophyte on goats is unknown at present. Prussic acid and high nitrates in summer annuals are more examples of anti-quality components, as is tannin content in lespedeza. Therefore, when anti-quality components are present in a forage plant, chemical assays to predict performance will usually overestimate the actual animal performance.

Principles of Forage Management

"Manage for maximum leaf production to maximize forage quality." This rule of thumb has been used for years. The principles that make this true are the bases for successful grazing management. When used, this principle typically refers to forage grasses, alfalfa, and other forage legumes such as lespedeza, clover, and birdsfoot trefoil. However, the principle holds true for herbaceous forbs (weeds?) such as pigweed, and brushy species such as blackberry briars.

Although goats are basically browsing animals, with preferred diets that are more similar to deer than cattle or sheep, most goat production involves grass based forage systems. The following discussion is based on forage grasses, but the principles would be the same for forbs, legumes, and brushy species. Only the location of the growing points and the way leaves form and grow would be different.

The basic unit of forage production is a tiller, which is composed of the leaf blade and sheath, stem, and seedhead. Tillers grow from the base up, and new leaves are pushed up through surrounding sheaths of older leaves. The last leaf to emerge is the flag leaf. The flag leaf precedes the emergence of the seedhead and is recognized by its peculiar orientation, generally parallel to the ground. Most forage grasses will produce between 5 and 10 leaves per tiller.

However, not all tillers become reproductive and produce a seedhead. Seedhead production varies from species to species and seasonally within species. Tall fescue makes a good example. Spring growth tillers, in response to cold temperatures and day length, produce seedheads while fall growth tillers generally remain vegetative. Bahiagrass, on the other hand, produces seedheads throughout its growing season (grievously so in a home lawn).

Individual tillers are relatively short-lived. New tillers originate from growing points or basal buds, a form of specialized plant tissue. If growing points are removed by grazing or cutting, no more tillers are produced. Most of the forage grasses, which have evolved under grazing, have basal buds at or slightly below the soil surface while broadleaf plants, including many of the brushy browse species preferred by goats have buds or growing points above ground.

Influence on Forage Quality

As the grass tiller changes from vegetative growth (leaf production) to reproductive growth (seedhead production) the plant goes through rapid physiological changes. Typically the plant attempts to place its seedhead up high so the seed can be dispersed over a wide area - it is trying to reproduce itself. This is seen as the stem elongates, called jointing in small grains. To hold the seedhead up the stem must become more rigid, stronger, stiffer, and tougher. These words indicate that digestibility or forage quality is decreasing. Fibers in the stem are being converted from more digestible forms to lignin the most indigestible form. The process of fiber conversion is occurring in all forages as they mature or age, even if the individual tiller does not become reproductive.

If the tiller is producing a seedhead, several other changes are occurring in the plant. Since all the leaves have already been produced by that tiller, the nutrients to fill the seed have to come out of these leaves. These nutrients include protein, minerals, and carbohydrates such as starches and sugars. The bottom, or oldest leaves on the tiller are the first to have nutrients translocated to the seedhead. When growing a grain crop, such as grain sorghum or wheat, we speak of the bottom leaves as 'firing.' The leaves are, in fact, senescing or dying. The translocation of nutrients is a great process when producing grain such as corn, wheat, or grain sorghum. Contrarily, most grass seed (including grain sorghum and the small grains, and especially the forage grass seeds) are relatively indigestible when fed whole and are generally passed out the rear of the animal and are useful only to birds!

This gives us two management principles then to help keep forage quality high. One is to harvest, graze or cut for hay, before seedheads are produced. The second is to utilize the forage in a way that maximizes the leaf:stem ratio.

Influence on Forage Quantity

On a per tiller basis, forage quantity increases as new leaves emerge. In general, maximum dry matter yield per tiller will occur sometime between flag leaf and flowering. Keep in mind that the plant must flower before the seed is formed so we are talking about the time before grain filling, soft dough, etc. However, maximum digestible nutrient yield almost always occurs at flag leaf, or before seedhead emergence.

While yield per acre does increase as tillers grow, yield mainly increases as the number of tillers per acre increases. New tillers are produced in response to several actions. Generally, removal of top growth will stimulate tillering, as long as the basal bud is protected. Proper fertility is needed for maximum tiller development as is reasonable moisture.

Energy, in the form of carbohydrates stored in roots and the lower stem bases, is used by the plant to develop new tillers. The new tiller uses this stored energy to 'feed' its new growth until it develops enough leaf area to produce its own energy or food. After that time the depleted energy in the roots is replaced. Depleted root energy reserves will slow new tiller development; therefore, proper defoliation management to keep root energy reserves replenished will maximize new tiller development and increase yield per acre.

In most forage grasses some sunlight needs to strike the basal bud to initiate new tiller development. This principle is the reason yield per acre can actually decrease if the defoliation period is too long. The grass actually mulches itself so to speak. Heavy growth does not allow sunlight to the growing points, bottom leaves are senescing, seedheads are forming, and, with no defoliation at all, total yield per acre decreases; and forage quality decreases.

This gives us two management principles to increase yield. Do not defoliate so frequently that root energy reserves are not replenished (stated another way, allow the forage plant time to grow with no grazing so that energy is moved to and stored in the roots). The second principle is to defoliate before the plant becomes decadent and few new tillers are being produced. This usually coincides with seedhead formation, and/or as a good percentage of the bottom leaves are senescing.

Understanding tiller growth and development is the key to proper defoliation management. Pastures should be grazed and hay can be cut to produce the desired or needed forage quality, through an understanding of the influence that defoliation has on forage quality and yield.

Application to Grazing Management

Grazing management is the application of basic plant and animal science principles to obtain the needed animal nutrition - quality and quantity – while maintaining the long term productivity or health of your pasture. You do this by controlling the intensity and frequency of forage plant defoliation. Intensity refers to the degree of defoliation, usually thought of as a stubble height. It is easy to visualize in a hay field, you cut the forage to a certain level, say leaving a 3 inch stubble in the field. Animal grazing can be manipulated to also leave a certain stubble height in the field. Frequency refers to how often a forage plant is grazed.

Since we speak in terms of controlling intensity and frequency of defoliation by controlling animal access to forage, we can reasonably refer to a controlled grazing system. The system uses cross fences to subdivide an area into multiple paddocks. Animals are rotated from one paddock to another to provide forage of a needed quality, depending on the class of animal (dry does, young growing animals, etc.).

To develop a grazing system the manager must know the number of grazing systems needed, the size of an area to put into a grazing system, the number of paddocks per system, the time to keep animals confined to one paddock, and the time to complete one rotation through all paddocks.

Your operation has a specific forage base at present; stocking rates for cattle are probably known and this will allow you to make a good estimate of goat carrying capacity.

A short, brief summary: put your goats on young forage to meet their nutritional needs, graze the paddock uniformly by adjusting goat numbers or by adjusting paddock size, move (rotate) them when they have defoliated the area to a desired stubble height and before they start grazing regrowth (replace root energy reserves), rotate back to the first paddock before it has become too mature to meet goat nutritional requirements.

Keep in mind that continuous grazing is a form of grazing management and it can meet certain production management objectives, particularly if the goat enterprise is just supplemental to a cattle or other operation.

Application to Brush and Weed Control

As mentioned previously goats actively prefer several plants that are considered weeds in typical Southeastern pastures; e.g., dewberry/blackberry briars, thistles, honeysuckle, kudzu, etc. By using the principles discussed earlier you can control unwanted weed and brush species in your pastures. To accomplish this, use the goats to defoliate the undesirable species by grazing off growing points frequently and intensively enough to deplete root energy reserves! This will usually require fairly high stocking rates.

If you are grazing goats on brush and weeds, weed control should be the primary management objective. Typically goats used for this purpose, as heavily as they are needed, will not perform well in terms of weight gain, milk production, or speed of rebreeding. It is thought, but not experimentally proven, that goats can be used to suppress weeds in a pasture without a severe decrease in performance. This would be accomplished by adjusting stocking rates, and the intensity and frequency of defoliation of the target weed species. This process should be helped by the goat's preference for most weeds. However, not all weeds are readily consumed by goats (e.g. Carolina horsenettle) and other means of weed control may have to be integrated into the management plan.

A final warning here; most of the brush/weeds that goats prefer are fairly nutritious, some more than the pasture grass. Properly utilized the weeds will produce reasonable goat performance. If you do indeed control the weeds with goats, you may find that you wish you had some of them back. Decide your objectives and manage the forage base (which may include the weeds) accordingly. Proper utilization of the brush/weeds so as not to kill them may result in under utilization of the forage grasses, due to goat browsing preferences.